This patch adds the ability for a userspace program to request an extend oflast cluster group on an Ocfs2 file system. The request is made via ioctl,OCFS2_IOC_GROUP_EXTEND. This is derived from EXT3_IOC_GROUP_EXTEND, but isobviously Ocfs2 specific.

tunefs.ocfs2 would call this for an online-resize operation if the lastcluster group isn't full.